The leukotrienes constitute a group of locally acting hormones, produced in living systems from arachidonic acid. The major leukotrienes are Leukotfiene B.sub.4 (abbreviated at LTB.sub.4), LTC.sub.4, LTD.sub.4, and LTE.sub.4. The biosynthesis of these leukotrienes begins with the action of the enzyme 5-lipoxygenase on arachidonic acid to produce the epoxide known as Leukotfiene A.sub.4 (LTA.sub.4), which is converted to the other leukotrienes by subsequent enzymatic steps. Further details of the biosynthesis as well as the metabolism of the leukotfienes are to be found in the book Leukotrienes and Lipoxygenases, ed. J. Rokach, Elsevier, Amsterdam (1989). The actions of the leukotrienes in living systems and their contribution to various diseases states are also discussed in the book by Rokach.
EP 385,662 describes a series of heterocycles differing notably from the present invention in not containing the bicyclic structure characterized by the oxygen and X.sup.1 bridges. EP 462,812 and 462,813 contain 5-membered heterocyclenes (Ar.sup.2) and a substituted phenylene (Ar), respectively. EP 462,830 and 462,831 lack and contain an oxygen attached to R.sup.1, respectively. However, none of the above compounds contains the bicyclic bridged structure of the present invention, characterized by the oxygen and X.sup.1 bridges.
Hence the compounds of the present invention are completely novel and unexpectedly have biological activity as leukotriene biosynthesis inhibitors. ##STR2##